Scientists from McMaster University in Canada have developed a dipstick that changes color when exposed to organophosphate pesticides. The test provides results in a matter of minutes, is reportedly inexpensive to produce, could be used for food testing, and perhaps might lead to a marketable product that one day could be found in food stores.
From the abstract in Analytical Chemistry:
A reagentless bioactive paper-based solid-phase biosensor was developed for detection of acetylcholinesterase (AChE) inhibitors, including organophosphate pesticides. The assay strip is composed of a paper support (1 x 10 cm), onto which AChE and a chromogenic substrate, indophenyl acetate (IPA), were entrapped using biocompatible sol-gel derived silica inks in two different zones (e.g., sensing and substrate zones). The assay protocol involves first introducing the sample to the sensing zone via lateral flow of a pesticide-containing solution. Following an incubation period, the opposite end of the paper support is placed into distilled deionized water (ddH2O) to allow lateral flow in the opposite direction to move paper-bound IPA to the sensing area to initiate enzyme catalyzed hydrolysis of the substrate, causing a yellow-to-blue color change. The modified sensor is able to detect pesticides without the use of any external reagents with excellent detection limits (bendiocarb ~ 1 nM; carbaryl ~ 10 nM; paraoxon ~ 1 nM; malathion ~ 10 nM) and rapid response times (5 min). The sensor strip showed negligible matrix effects in detection of pesticides in spiked milk and apple juice samples. Bioactive paper-based assays on pesticide residues collected from food samples showed good agreement with a conventional mass spectrometric assay method.
Abstract in Analytical Chemistry: Reagentless Bidirectional Lateral Flow Bioactive Paper Sensors for Detection of Pesticides in Beverage and Food Samples
Statement by the American Chemical Society: An inexpensive ‘dipstick’ test for pesticides in foods …